(1) Field of the Invention
The present invention relates to a process for preparing a tocopherol concentrate from a deodorized distillate formed as a by-product at the step of deodorizing oils and fats.
(2) Description of the Prior Art
.alpha.-, .beta.-, .gamma.- and .delta.-Tocopherols (hereinafter referred to as "tocopherols") are ordinarily contained in an amount of about 1 to about 20% by weight in a deodorized scum, deodorized sludge or hot well oil dreg (hereinafter referred to as "deodorized distillate") formed as a by-product at the step of deodorizing oils and fats such as soybean oil, linseed oil, cotton seed oil, safflower oil, rice bran oil, corn oil and sunflower oil. Accordingly, the deodorized distillate is valuable as the material for production of vitamin E or an antioxidant. However, this deodorized distillate contains 30 to 60% by weight of free fatty acids, 10 to 35% by weight of sterols and esters thereof, 10 to 30% by weight of hydrocarbons, 10 to 20% by weight of glycerides and several % by weight of other substances in addition to tocopherols. Accordingly, in order to obtain a tocopherol concentrate from such deodorized distillate, it is important to remove these substances, especially free fatty acids.
Various processes have heretofore been proposed for obtaining tocopherol concentrates from deodorized distillates. For example, Japanese Patent Publication No. 23147/70 discloses a process for the preparation of tocopherol concentrates which comprises subjecting a deodorized distillate to a halogenohydrogenation treatment for separating and removing sterols and then to distillation. However, since a hydrogen halide is used in this process, the operation is not preferred, and furthermore, since removal of free fatty acids is not intended, the concentration of tocopherols in the obtained concentrate is low and no satisfactory product is obtained.
As another known process, there can be mentioned an ester exchange process comprising ester-exchanging a deodorized distillate with methanol, subjecting the ester exchange product to distillation to remove free fatty acids in the form of methyl esters and concentrating the residue by molecular distillation or the like. In this process, since the deodorized distillate and methanol are heated and refluxed with a strong acid catalyst such as hydrochloric acid or sulfuric acid for a long time, by-products are readily formed, and the viscosity of the residue left after removal of methyl esters of fatty acids by distillation is high and therefore, the operation efficiency is reduced at the subsequent step of concentration by molecular distillation or the like.
As still another known process, there can be mentioned a methyl esterification process comprising saponifying a deodorized distillate, converting the saponified deodorized distillate to a methyl ester and carrying out distillation and concentration as in the ester exchange process. The operation of this process is complicated, and since tocopherols are unstable against alkali, there is a fear of loss of parts of tocopherols during the operation. Furthermore, the same defects as mentioned above with respect to the ester exchange process arise at the steps of distillation and concentration.
Furthermore, there can be mentioned a process in which a deodorized distillate is directly subjected to distillation and fractions are cut to remove free fatty acids. This process, however, is defective in that the viscosity of the distillation residue is high as in the above-mentioned two processes.